昌宁出土铜镯的工艺及合金成分分析

Metallographic microscopy and alloy composition analysis of bronze bracelets from Changning

铜镯是“西南夷”地区青铜时代最为常见的青铜器种类之一,考古发现数量众多,造型和纹饰因地而异。这种装饰品对于研究青铜时代西南先民的青铜艺术、技术等具有重要的价值。之前关于西南夷青铜器的研究,更多集中于铜鼓、铜兵器等主要铜器类型,而专门对铜镯展开的专题研究较少,因此目前对云南各地域铜镯的合金成分与制作技术特征缺乏整体性认识。与此同时,由于铜镯是一类常见的装饰品,对其进行研究可更直接地反映不同文化人群对金属资源的掌控、青铜技术的选择等考古学问题。根据文献记载,云南西部保山昌宁一带是西南夷中哀牢的主要分布区,近年来对该地展开的考古发掘工作为研究哀牢青铜文化提供了科学的实物资料。为了探讨昌宁地区哀牢青铜文化铜镯的合金成分及制作工艺特点,深化对云南不同地区出土铜镯技术特征的认识,本研究利用金相显微镜和扫描电镜能谱仪对昌宁出土的6件铜镯进行了成分分析和金相观察。结果显示,此批铜镯全部为锡青铜,含有少量的砷、硫、锑等杂质元素;其制作工艺多样,铸造、热锻和热锻后冷加工等多种方法并用。在此基础上,收集云南其他地区出土铜镯的科技分析数据,并结合类型学展开对比分析,把握各地铜镯制作技术的差异和联系。结果表明,云南各地出土铜镯,均以锡青铜为主,制作工艺上铸锻并重,这反映了西南夷青铜技术体系的一个重要特征。但进一步观察发现,铜镯的合金配比和加工方式又表现出明显的当地特色,如哀牢铜镯的平均含锡量最高且十分稳定,而滇、昆明夷铜镯的锡含量范围非常离散。各西南夷族群所采用的铜镯制作方法的同与异,究其原因,可能和铜镯造型、族群对资源的掌控能力、人的审美喜好等方面有关。本研究的创新性在于从铜镯这一被较少关注的青铜器类出发,结合成分、金相与类型学分析,综合以往研究对云南各地域出土铜镯工艺技术的共性及区别展开讨论。总之,铜镯作为云南地区常见的人体装饰品,不仅展现了不同区域少数民族对铜镯这一器型采用的合金配比与青铜制作工艺,而且从非实用器的角度反映了西南夷对资源的利用与掌控、审美思想等方面的信息。

One of the most common types of bronze wares during the Bronze Age in the“Southwest Yi”region were bronze bracelets,which have been found in large numbers through archaeological excavations,with shapes and decorations varying from place to place.This ornament is of great value for the study of the art and technology of ancestors in southwest China during the Bronze Age.Previous research on bronze wares in southwest China has focused more on their main types,such as bronze drums and weapons,but there is little thematic research on bronze bracelets.Therefore,the overall knowledge of alloy compositions and technical characteristics of bronze bracelets from various regions of Yunnan is not sufficient.Furthermore,because bracelets are a kind of common ornament,the study of bracelets can more directly reflect archaeological issues such as the control of metal resources and the selection of bronze techniques by different cultural groups.In recent years,archaeological excavations carried out in the area around Changning County of Baoshan in western Yunnan,which is documented to be the main distribution area of the Ailao of the Southwest Yi,have provided scientific and physical materials for the study of the Ailao bronze culture.In order to explore the alloy composition and manufacturing technique of bronze bracelets of the ancient Ailao culture in Changning region and learn more about the technical characteristics of bronze bracelets in different regions of Yunnan,six bronze bracelets unearthed in Changning were analyzed using metallographic microscopy and scanning electron microscopy-energy dispersive spectrometry(SEM-EDS).The results show that all the bracelets are tin bronzes containing small amounts of As,S,Sb and other impurity elements.The manufacturing techniques are varied.Some of the bronzes analyzed were cast metal,some pieces were hammered,and others were processed by cold working after being hammered.On this basis,the scientific and technological analysis data of bronze bracelets unearthed in other areas of Yunnan were collected and compared by typology to grasp the differences and connections between the techniques of bronze bracelets in each region.The analysis shows that the bracelets in all parts of Yunnan indicate relatively consistent technical characteristics.Most of them were tin bronze and were made by casting or forging.This reflects the important feature of the Southwest Yi bronze technical system.However,further observations reveal that the alloy compositions and manufacturing techniques of the bronze bracelets show local characteristics,such as the highest and stable tin content of the bronze bracelets from Ailao,while the range of tin content in the bronze bracelets from Dian and Kunming Yi are very discrete.It also shows strong regional characteristics,which may be related to vessel types and natural resources,etc.The innovation of this study is to discuss the commonalities and differences between the techniques used in bronze bracelets excavated in Yunnan in the context of compositional,metallographic,and typological analyses of a less studied bronze category.In a word,as a common body ornament in Yunnan,bronze bracelets not only demonstrate the alloy compositions and manufacturing techniques of ethnic groups in different regions,but also reflect the utilization and control of resources and the aesthetic ideology of the Southwest Yi from a non-utilitarian perspective.